1. Field of the Invention
The present invention relates to the art of water treatment systems. More particularly, the present invention is directed to an apparatus for dissolving potassium permanganate (KMnO.sub.4) crystals in water to produce a uniform saturated potassium permanganate solution and for dispensing the solution to regenerate manganese oxide based iron removal water treatment systems.
2. Description of Related Art
Iron dissolved in water used for residential and commercial purposes can cause problems which make its removal desirable. For example, water with a high iron content can cause rust stains on clothing and plumbing fixtures and can make food and beverages taste unpleasant.
One commonly used method for removing iron from water involves flowing a stream of the water through a mineral bed containing "manganese greensand," a material consisting of small pebble-like particles coated with manganese oxide (MnO.sub.2). The manganese greensand oxidizes the dissolved iron, thereby allowing the iron to precipitate in a solid form which can be filtered out. However, this oxidation process gradually exhausts the water treatment capability of the manganese greensand, so that its ability to remove iron from water becomes degraded. When this occurs, the manganese greensand may be regenerated by exposing it to a solution containing an appropriate oxidizer most commonly potassium permanganate, which process restores its iron removal capability. Typically, the regeneration process is performed automatically at periodic intervals to prevent the mineral bed from ever becoming completely exhausted.
Typically, a feeder provides the potassium permanganate solution needed for regeneration. A number of different feeder designs are known. Generally, a quantity of potassium permanganate crystals sufficient to supply many regenerations is placed in the feeder. Water is added to the feeder to dissolve a portion of the potassium permanganate crystals, and the feeder is able to dispense the resulting solution to the iron removal system.
For the manganese greensand to be fully regenerated by the regeneration process, it must be exposed to a solution having a sufficient amount of potassium permanganate present therein. This, in turn, means that the feeder must dissolve this sufficient amount of potassium permanganate and dispense the solution to the iron removal system. One way to ensure that a sufficient amount of potassium permanganate is provided for regeneration is to add a known amount of water to the feeder containing potassium permanganate crystals, so that potassium permanganate solution having a known saturation is formed, and then to dispense all of this solution for regeneration.
However, it is difficult to form a saturated potassium permanganate solution, and it is especially difficult to achieve a uniform level of saturation with each regeneration as the amount of potassium permanganate crystals present in the feeder decreases. Specifically, in many feeder designs the level of saturation decreases as the amount of potassium permanganate crystals decreases.
One way of achieving a more uniform saturation is to wait a long period of time after adding the water to the feeder before dispensing the solution. However, with many iron removal systems this is not possible because the automatic regeneration process applies suction to the feeder to withdraw solution almost immediately after the water is added to the feeder. With such a short amount of time to dissolve the potassium permanganate, it is particularly difficult to provide a uniform saturated solution.
The handling of potassium permanganate also presents a number of additional difficulties. Potassium permanganate is very reactive and, over time, tends to corrode or degrade many common materials. It also stains skin, clothing, and other materials and is damaging to the environment. Accordingly, it is crucial that any leakage or spillage of potassium permanganate crystals or solution be minimized.